With the advent of touch-sensitive interfaces on the screen of computing devices, it has become necessary to find alternative human-computer interfaces to the traditional keyboard and mouse. Many of these devices, often referred to as tablet computers, smart phones, and smart screens, don't support the traditional input paradigms of an external keyboard and mouse. Rather, they rely on the direct input of the user through human touch.
Besides this type of computing device, there are also other touch-interface devices that use a similar mode for user input. One such example is that of a touch-sensitive computer keyboard that is made up of a solid touch-sensitive surface that can be easily wiped for cleaning purposes.
Traditionally, these touch sensitive surfaces respond immediately to the user's touch (or release). The paradigm is simple: point, touch, select. While this works well for many applications, it is problematic in situations where the user desires to rest their hands and/or fingers on the surface. A touch sensitive keyboard (onscreen or stand-alone) is a good example of such a situation; a trained ten-finger touch typist relies on resting their fingers on the home row of the keyboard and then pressing keys to initiate an action. On traditional touch surfaces, this isn't possible because as soon as the user touches the surface to rest their fingers, an action is initiated. These solutions don't take into account the need for the user to rest their hands/fingers on the surface.
There are many methods for detecting the touch of a human user, including sensors based on capacitance, infrared light, resistance, surface acoustic waves, and force sensors. Each of these methods have their respective advantages and disadvantages. But the vast majority of today's touch-based systems have standardized on using touch capacitance.
An example of one of the first uses of a touch capacitance for computer input is described in U.S. Pat. No. 5,305,017 to Gerpheide. This approach has become the standard for providing a cursor-pointing alternative to a computer mouse in the form of a touchpad, commonly included in most laptop computers. The method decodes touches in two dimensions, offering offsets in the horizontal (x) direction and vertical (y) direction as the user moves their finger across the touchpad surface. However, no consideration is given to user assertions in the vertical (−z) direction.
This approach to sensing human touch using changes in capacitance is commonly employed in the industry. Electronic chips are readily available to perform these functions, such as the QT60486 from Quantum Research Group and the AT32UCL3L from Atmel Corporation. These chips, and others like them, are used by hundreds of companies to sense human touch.
Others have taken the concept of touch capacitance input further to include decoding user gestures and assigning functions to them. U.S. Pat. No. 7,470,949 by Jobs et al. teaches how gestures using simultaneous touches on a capacitive surface such as “pinching”, rotating, and swiping can be used to manipulate onscreen elements. While this approach allows for multiple fingers touching the surface at one time, it is not for the purpose of allowing the user to “rest” their fingers on the surface, but rather for a specific intended action to be performed.
The object coming into contact with the touch sensitive surface may not always be a human finger. For example, other forms of touch sensors such as resistive, surface acoustic wave, and infrared allows passive objects such as a plastic stylus to be used to make selections on the touch surface. It is possible to also apply this concept using capacitive sensors, by designing input objects with capacitive properties similar to a human finger. For example, in U.S. Pat. No. 5,488,204 Mead et al. describe a paintbrush-like input device that is capable of creating brush-like strokes on a display screen. Mead further teaches using X and Y sensor data to determine a Z-value representing finger pressure. Mead's teachings build on the teachings of Miller et al. in U.S. Pat. No. 5,374,787. This method, however, is targeted toward a single input (of either a single finger, stylus, or paintbrush-like input device) and is focused on a touchpad rather than a touch surface that is part of a display or graphical surface. It doesn't apply the concept to the problem of multiple fingers resting directly on the touch surface on which are displayed actionable regions, as disclosed in the present invention.
There are numerous other devices that use force sensors to detect pressure in the Z direction. For example, in U.S. Pat. No. 8,026,906 Molne et al. describe using force-sensing resistors (FSR's) to measure downward pressure on a touch screen, wherein the FSR's are placed between the touch sensitive surface and supporting posts (or feet at all four corners). In U.S. Pat. No. 5,241,308 Young et al. describe a similar method wherein pressure is detected by the deformation between two panels closely spaced apart, or by providing force-sensing means located at each of the spaced apart support. These devices measure the forces transmitted by the touch surface to a fixed frame at multiple points (see also U.S. Pat. No. 3,657,475 to Peronneau et al. and U.S. Pat. No. 4,121,049 to Roeber). These methods detect pressure by a means that is separate from the means to detect touch, whereas the present invention detects touch, resting, and pressing all through the same touch capacitive means.